Hooklifts, otherwise known as hooklift hoists, generally relate to equipment mounted on heavy duty trucks that allow hauliers in the truck cab to lift, re-position, transport, and unload or dump various pieces of heavy equipment. The lifted equipment is usually a tilt-frame body, pallet, flat rack, flatbed, bin, dumpster body, and other similar heavy containers. The containers that are changed out by the hooklift are often specialized containers used for the transportation of materials in various industries, and particularly in waste, recycling, snow removal, scrap, and demolition industries. Hydraulic hooklift hoist systems offer several advantages, including ground level loading and unloading, exact positioning in dropping off containers, ability to get in and out of tight spaces, quick exchange of containers, and complete in-cab operation.
To change out a container on a hooklift, the hooklift system typically employs a series of hydraulic rams to hook the container, and then subsequently lift and hoist the container onto the chassis of a heavy duty truck designed to operate the hooklift. The container is then secured onto the truck and transported to another location where the container can be dumped or unloaded and the hooklift is then free again to hoist and transport another body or container.
A hooklift system is generally made up of the heavy duty truck, a hydraulic system, a jib system, and a hook.
Lift and dump capacities of hydraulic hooklift hoists typically range from 8,000 to 68,000 pounds, which varies according to the properties of the truck chassis and the containers themselves. In achieving the desired load capacity, the ratio of container length to chassis length must be considered to determine the load angle. Hooklift hoist systems indicate a recommended range of body lengths, and container bodies that are shorter than the recommended length produce substantially steeper load angles, and consequently lower load rating, than those of the longest bodies intended for use with a particular hoist. The chassis frame height is also important, as the lower the chassis frame height, the lower the potential load angle. To achieve the optimal load capacity, a combination of low chassis with the longest recommended body length should be used. Additionally, the hook height has an effect on load capacity, as a taller hook height achieves a greater lift and dump capacity. The hydraulic operating pressure of hooklifts is preset to achieve the intended lifting capacity for the design application.
There are two common types of jib system, each controlled by a single hydraulic cylinder and which can be used with either a single or dual rear pivot section. An articulating jib, also referred to as a tilting jib, is a simple A-frame. When extending the cylinder, the container or body is pushed up and back, exiting the rear locks. When retracting the cylinder, the container or body is pulled forward and down, engaging the rear locks. On the other hand, a sliding or telescoping jib consists of a single arm composed of a tube within a tube. When extending the cylinder, the container or body is pulled forward, engaging the rear locks. When retracting the cylinder, the container or body is pushed rearward, exiting the rear locks.
Traditional hooklifts use two hydraulic cylinders to actuate the motion of the hooklift to move backwards and connect to the item it will pull onto the truck or trailer: the lift/dump cylinder and the tilt cylinder.
The lift/dump cylinder not only lifts the body or container onto the truck, but it also provides the dumping movement in unloading the container. There are also two typical configurations of the lift/dump cylinder. The single lift/dump cylinder design reduces unit cost, retains true hooklift capabilities, but can be unstable while dumping on uneven ground. On the other hand, the dual lift/dump cylinder design increases unit cost, but improves load handling stability when dumping on uneven ground. Dual counterbalance valves can provide for increased meter-ability and protection against sudden movement in the case of hose failure.
A tilt cylinder is also present to operate the tilt section of the hooklift. It is a key component of the hooklift as it provides the selection of dump or load/offload. It has both extend and retract sides to allow for this functionality.
This double hydraulic base system to control the rotational movement of the arm or jib and to reduce the load angle of any attachment is very expensive, particularly because it must be installed onto a truck chassis specific to the design specifications of the hooklift base system and the application for which it is used.